U.S. patent number 4,540,725 [Application Number 06/641,350] was granted by the patent office on 1985-09-10 for pigment grinding vehicle.
This patent grant is currently assigned to PPG Industries, Inc.. Invention is credited to Robert D. Jerabek, Mark W. Johnson, Jeffrey G. Koren.
United States Patent |
4,540,725 |
Jerabek , et al. |
September 10, 1985 |
Pigment grinding vehicle
Abstract
A quaternary ammonium group-containing material which is
obtained from reacting a polyepoxide with an amine containing at
least one acyclic group of about 8 to 30 carbon atoms and
optionally an amine containing an alkylarylpoly ether moiety is
disclosed. The resins are useful as pigment grinding vehicles and
in the formulation of pigment paste, particularly pigment paste
with high pigment loadings. When formulated into cationic
electrodepositable compositions, the pigment grinding vehicles
provide for cured electrodeposited coatings of excellent corrosion
resistance, particularly over untreated and oily steel.
Inventors: |
Jerabek; Robert D. (Glenshaw,
PA), Koren; Jeffrey G. (Butler, PA), Johnson; Mark W.
(Gibsonia, PA) |
Assignee: |
PPG Industries, Inc.
(Pittsburgh, PA)
|
Family
ID: |
27028474 |
Appl.
No.: |
06/641,350 |
Filed: |
August 15, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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430185 |
Sep 30, 1982 |
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Current U.S.
Class: |
523/400; 523/351;
528/114; 528/120; 528/121; 564/287; 564/292; 564/294 |
Current CPC
Class: |
C09D
17/00 (20130101); C08G 59/14 (20130101) |
Current International
Class: |
C08G
59/00 (20060101); C09D 17/00 (20060101); C08G
59/14 (20060101); C08L 063/00 () |
Field of
Search: |
;523/400,351
;528/120,121,407,114 ;260/404 ;564/292,294,295 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
NEO-FAT.RTM. Fatty Acids Manual--by Armak Chemicals Division
(1971), see pp. 15-17..
|
Primary Examiner: Jacobs; Lewis T.
Attorney, Agent or Firm: Akorli; Godfried R.
Parent Case Text
This application is a continuation of application Ser. No. 430,185,
filed Sept. 30, 1982, abandoned.
Claims
What is claimed is:
1. A quaternary ammonium group-containing material which is
obtained from reacting:
(i) a polyepoxide having a 1,2-epoxy equivalency greater than
one,
(ii) an amine containing at least one organic group which contains
an acyclic moiety of about 8 to 30 carbon atoms, and
(iii) an amine containing an alkylarylpolyether moiety of the
formula: ##STR6## wherein R is an alkyl group containing from 1 to
30 carbon atoms, R' is hydrogen or lower aklyl containing from 1 to
5 carbon atoms and x is equal to 3 to 20,
under conditions sufficient to form the quaternary ammonium group;
the equivalent ratio of (i):(ii):(iii) is about 1:0.4 to 1:0.1 to
0.6 and the equivalent ratio of (i):(ii)+(iii) is equal to or
greater than 1.
2. The quaternary ammonium group-containing material of claim 1,
wherein the polyepoxide is a polyglycidyl ether of a polyol.
3. The quaternary ammonium group-containing material of claim 2,
wherein the polyepoxide is a polyglycidyl ethter of bisphenol A,
having an epoxy equivalent of about 100 to 500.
4. The quaternary ammonium group-containing material of claim 1,
wherein the amine is of the structure: ##STR7## wherein R.sub.1,
R.sub.2 and R.sub.3 are alkyl groups of which at least one group
contains from about 8 to 30 carbon atoms, and at least one group is
methyl.
5. The quaternary ammonium group-containing material of claim 4
wherein two groups are methyl and one group contains from 8 to 30
carbon atoms.
6. The quaternary ammonium group-containing material of claim 4,
wherein the amine is N-octadecyldimethylamine.
7. The quaternary ammonium group-containing material of claim 1,
wherein the amine containing an alkylarylpolyether moiety is
derived from the reaction product of:
(i) an alkylarylpolyether alcohol,
(ii) an organic diisocyanate, and
(iii) a hydroxyl-containing tertiary amine.
8. A pigment grinding vehicle comprising the quaternary ammonium
group-containing material as recited in claim 1 which is at least
partially acid-neutralized.
9. A pigment paste comprising:
(A) the grinding vehicle of claim 8,
(B) a pigment dispersed in (A).
10. A pigment paste of claim 9 wherein the weight ratio of (B) to
(A) is at least 10:1.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition of matter useful as
a pigment grinding vehicle and to pigment pastes formulated with
such pigment grinding vehicles.
2. Brief Description of the Prior Art
In the formation of paints and especially electrodepositable
paints, an important factor is the introduction of pigments into
the paint. Pigments are typically ground with a grinding vehicle to
form a pigment paste. The resultant paste is then combined with the
film forming resin and optional ingredients to form the paint,
giving the paint the proper color, or opacity, and application or
film properties.
A problem with many pastes used for electrodeposition is the
relatively low ratio of pigment to grinding vehicle which can be
used. In cationic electrodepositable paints, pigment to grinding
vehicle weight ratios are typically 5 to 1 or less. Pastes with
higher ratios are not stable. Also, many pigment grinding vehicles
do not contribute to, and may actually detract from some of the
desirable properties of the resultant coating, particularly the
property of corrosion resistance.
The present invention provides for pigment grinding vehicles which
can be used to formulate a stable pigment paste having a relatively
high pigment to grinding vehicle weight ratio. Also the instant
pigment grinding vehicles enhance the corrosion resistance of the
resultant coating.
SUMMARY OF THE INVENTION
In accordance with the foregoing, the present invention encompasses
a quaternary ammonium group-containing material which is obtained
from reacting:
(i) a polyepoxide having a 1,2-epoxy equivalency greater than one,
and
(ii) an amine containing at least one organic group which contains
an acyclic moiety of from about 8 to 30 carbon atoms, and
preferably
(iii) an amine containing an alkylarylpolyether moiety of the
formula: ##STR1## wherein R is an alkyl group containing from 1 to
30 carbon atoms, R' is hydrogen or lower alkyl containing from 1 to
5 carbon atoms, and x is equal to 3 to 20,
under conditions sufficient to form the quaternary ammonium
group.
The instant compositions of matter have been found useful as
pigment grinding vehicles. Accordingly, the present invention
encompasses pigment pastes containing the instant composition of
matter as a grinding vehicle, and a pigment or pigments dispersed
therewith. While these pastes can be useful in inks and many types
of coatings, they are particularly useful in cationic
electrodeposition compositions.
DETAILED DESCRIPTION OF THE INVENTION
The useful polyepoxides can be monomeric or polymeric compounds or
mixture of compounds having a 1,2-epoxy equivalency greater than
1.0, preferably greater than 1 and up to 4.0. It is preferred that
the organic polyepoxide be polymeric or resinous and have a
1,2-epoxy equivalent of about 100 to 500.
A preferred class of polyepoxides are the polyglycidyl ethers of
polyphenols, such as bisphenol A. These may be prepared, for
example, by etherification of a polyphenol with epichlorohydrin or
dichlorohydrin in the presence of an alkali. The phenolic compound
may be bis(4-hydroxyphenyl) 2,2-propane;
4,4'-dihydroxybenzophenone; bis(4-hydroxyphenyl)1,1-ethane;
bis(4-hydroxyphenyl)1,1-isobutane;
bis(4-hydroxy-tertiarybutylphenyl)2,2-propane;
bis(2-hydroxy-naphthyl)methane; 1,5-hydroxy-naphthalene; or the
like. Another quite useful class of polyepoxides are produced
similarly from novolak resins or similar polyphenol resins.
Also suitable are the similar polyglycidyl ethers of polyhydric
alcohols which may be derived from such polyhydric aliphatic
alcohols as ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol,
1,2,6-hexanetriol, glycerol, bis-(4-hydroxycyclohexyl)2,2-propane,
and the like.
There can also be employed polyglycidyl esters of polycarboxylic
acids which are produced by the reaction of epichlorohydrin or a
similar epoxy compound with an aliphatic or aromatic polycarboxylic
acid, such as oxalic acid, succinic acid, glutaric acid,
terephthalic acid, 2,6-naphthalene dicarboxylic acid, dimerized
linoleic acid and the like. Examples are diglycidyl adipate and
diglycidyl phthalate.
Also useful are polyepoxides derived from the epoxidation of an
olefinically unsaturated alicyclic compound. These polyepoxides are
nonphenolic and obtained by epoxidation of alicyclic olefins, for
example, by oxygen and selected metal catalyst, by perbenzoic acid,
by acid-aldehyde monoperacetate or by peracetic acid.
The amines useful herein are preferably tertiary amines and are
those which are capable of reacting with and opening the epoxide
moiety in the presence of acid and/or water. The useful amines
contain at least one lower alkyl group of from 1 to 4 carbon atoms,
preferably methyl, and at least one organic group which contains an
acyclic moiety of from about 8 to 30, preferably 12 to 18 carbon
atoms. Preferably, two of the groups are methyl and the other one
is an organic group containing an acyclic group of from about 8 to
30, preferably 12 to 18 carbon atoms.
The term "organic group" as used herein is intended to encompass
saturated and unsaturated groups, as well as substituted and
unsubstituted hydrocarbyl groups, provided that the substituent
does not adversely affect the reaction of the tertiary amine or the
performance of the instant compositions derived therefrom. Examples
of substituents would be hydroxy groups and alkoxy groups. Also,
the acyclic group can contain moieties in the chain such as ether
and ester groups.
Examples of the tertiary amines are those represented as: ##STR2##
wherein R.sub.1, R.sub.2, and R.sub.3 are alkyl groups of which at
least one group contains, each independently, from about 8 to 30
carbon atoms, and at least one group is a lower alkyl containing
from 1 to 4 carbon atoms, preferably methyl. Preferably, one of the
alkyl groups contains an acyclic moiety containing from about 8 to
30, and more preferably from about 12 to 18 carbon atoms, and two
of the groups are lower alkyl containing from 1 to 4 carbon atoms,
preferably methyl. Illustrative examples of the useful fatty amines
are N-octadecyldimethylamine, N-tetradecyldimethylamine,
N-octyldimethylamine, N-decyldimethylamine, N-dodecyldimethylamine
and N-nonyldimethylamine. It is expected that heterocyclic amines
in accordance with this invention will be useful herein.
The amine containing an alkylarylpolyether moiety is preferably an
organic tertiary amine. The organic amine contains an
alkylarylpolyether moiety, typical of which is represented by the
following structural formula: ##STR3## where R is an alkyl radical
containing from 1 to 30 carbon atoms and R' is hydrogen or lower
alkyl containing from 1 to 5 carbon atoms and x is equal to 3 to
20. Preferably, R is a branched alkyl group containing secondary,
tertiary, or both secondary and tertiary carbon atoms. In the most
preferred embodiment, R is octyl.
In the above structural formula, the aryl radical is represented by
the phenyl ring. It should be appreciated, however, that other aryl
radicals such as derived from naphthalene, anthracene, and
phenanthrene can be used.
In one embodiment of the invention, the organic amine containing an
alkylarylpolyether moiety can be prepared by reacting an
alkylarylpolyether which contains an active hydrogen such as
hydroxyl with an organic diisocyanate to form a half-capped
isocyanate product. An organic amine containing active hydrogens
such as a hydroxyl-containing tertiary amine can then be reacted
with a half-capped isocyanate to form the desired adduct. In a
preferred embodiment of the invention, toluene diisocyanate is
half-capped with an octyl phenol-ethylene oxide adduct having the
following structural formula: ##STR4## where x is equal to 12 to
13. The half-capped adduct is then fully capped with
dimethylethanolamine to form a tertiary amine adduct containing an
alkylarylpolyether moiety which also contains urethane
linkages.
The equivalent ratio of polyepoxide:amine containing at least one
lower alkyl group and 1 acyclic group of 8 to 30 carbon atoms:
amine containing alkylarylpolyether moieties can vary within the
following ranges --1:0.4-1.0:0 to 0.6, Preferably 1:0.4-0.9:0.1 to
0.6, and the equivalent ratio of polyepoxides to total amine being
equal to or greater than 1. The equivalents are based on epoxy
functionality and amine functionality, with the amines being
considered monofunctional.
With tertiary amines, the polyepoxides can be reacted by simply
mixing the two together, preferably in the presence of a controlled
amount of water. The amount of water employed should be that amount
of water which allows for smooth reaction of epoxy groups.
Typically, the water is employed on the basis of about 1.0 to about
16, preferably 2 to 10 moles of water per equivalent of amine
nitrogen.
The reaction proceeds at room temperature in most cases and, in
some cases, exothermically, so that moderate cooling may be
necessary. In some cases, moderately elevated temperature can be
used and is preferred. Typically, the reaction is conducted between
about 50.degree.C. and 100.degree. C. The reaction may be conducted
in the presence of a solvent if desired. If a solvent is employed,
preferably it is capable of being used in the ultimate composition
which is formed. For example, alcohols, ketones and glycol ethers
may be used.
The reaction of the tertiary amine(s) and polyepoxide is usually
conducted in the presence of acid and/or water under conditions
sufficient to form the quaternary ammonium salt or hydroxide. The
presence of water is preferred to moderate the reaction. The
presence of acid is preferred for pigment grinding. The amine(s)
can be first neutralized with acid to form the amine salt followed
by reaction with the polyepoxide. Alternately, the polyepoxide,
amine(s) and acid can be reacted simultaneously or the amine(s) and
epoxide can be first reacted followed by acidification.
The useful acids can be organic or inorganic acids preferably those
having a pKa less than 6. Preferably, the acid is water soluble,
and preferably it is organic. Examples of acids include phosphoric
acid, acetic acid and lactic acid.
To form the quaternary ammonium group, the use of tertiary amine(s)
is preferred. However, quaternary ammonium base group-containing
resins can be prepared with primary and secondary amines. This can
be accomplished by first reacting the primary or secondary amine(s)
with the polyepoxide. Reaction is continued until a tertiary amine
is formed. Further reaction with unreacted epoxy which may be from
the original polyepoxide or from externally added epoxy such as
propylene oxide, is continued to form the quaternary ammonium base.
When using primary or secondary amines, some precautions should be
taken to avoid gelling of the resin. For example, when
quaternization is effected through the polyepoxide moiety, the
molecular weight should be low and/or the epoxy equivalent weight
high to avoid gelling. Preferably, quaternization takes place from
externally added epoxy. Besides propylene oxide mentioned above,
the glycidyl esters and ethers of fatty acids and alcohols such as
the glycidyl ester of versatic acid can be used and their use is
preferred for superior pigment grinding properties.
Besides quaternizing with additionally added epoxy material,
alkylating agents such as dimethylsulfate and methyl iodide can be
used, but their use is less preferred, particularly in preparing
electrodeposition compositions.
The compositions of the invention have been found to be very
effective as pigment grinding vehicles. The grinding vehicles are
used to prepare pigment pastes containing one or more pigments
which are ground with the grinding vehicle. The pigment pastes are
prepared by grinding or dispersing the pigment into the grinding
vehicle in a manner well known in the art. The pigment paste
comprises as essential ingredients the quaternary ammonium pigment
grinding vehicle prepared as described above and at least one
pigment; however, the paste may, in addition, contain optional
ingredients such as plasticizers, wetting agents, surfactants or
defoamers.
Grinding is usually accomplished by the use of ball mills, sand
mills, Cowles dissolvers, continuous attritors and the like until
the pigment has been reduced to the desired size, preferably has
been wet by and dispersed by the grinding vehicle. After grinding,
the particle size is generally in the range of 10 microns or
less.
Preferably, grinding is conducted in an aqueous dispersion of the
vehicle. The amount of water present in the aqueous grind should be
sufficient to produce a continuous aqueous phase. The aqueous grind
usually contains about 30-70 percent total solids. The use of more
water merely reduces the effective capacity of the mill and, while
less water can be employed, higher resultant viscosity may create
problems in certain instances.
One of the advantages of the pigment grinding vehicles of the
present invention is their ability to be formulated into pastes
with high pigment to grinding vehicle weight ratios. Depending upon
the pigment to be dispersed, typical weight ratios of at least 10
to 1, preferably higher, that is, 15 to 40:1, can be attained
without the paste settling or separating when stored for 7 days at
120.degree. F. (49.degree. C.). Pigment pastes with lower pigment
grinding vehicle weight ratios that are as low as 1 to 1 can, of
course, be prepared.
Pigments which may be employed in the practice of the invention are
pigments well known in the art. Generally, titanium dioxide is the
sole or chief white pigment; other white pigments and/or extender
pigments including antimony oxide, zinc oxide, basic lead
carbonate, basic lead sulfate, barium carbonate, China clay,
calcium carbonate, aluminum silicate, silica, magnesium carbonate,
magnesium silicate, among others, may be used. Colored pigments may
also be employed, for example, cadmium yellow, cadmium red, carbon
black, phthalocyanine blue, chrome yellow, toluidine red, hydrated
iron oxide, among others.
The pigment paste can be combined with a film forming resin to form
a paint. The film forming resin can be a cationic resin known in
the art for electrodeposition. These resins are well known in the
art and need not be described in detail. Examples of suitable
resins include tertiary amine salt-containing resins such as those
described in U.S. Pat. No. 4,148,772 assigned to PPG Industries,
Inc., the assignee of the present invention; and quaternary
ammonium salt-containing resins such as those described in U.S.
Pat. No. 3,839,252 to Bosso et al. The portions of these references
which describe suitable electrodepositable resins for cationic
electrodeposition are hereby incorporated by reference.
Enough of the pigment paste is used so that the final
electrodepositable composition (electrodepositable resin plus
pigment paste) has the properties required for electrodeposition.
In most instances, the final electrodepositable composition has a
pigment-to-binder (electrodepositable resin plus pigment
dispersant) ratio of between about 0.05 to about 0.6.
For electrodeposition, a bath containing about 5-25 percent by
weight solids, that is, pigment plus resinous vehicle, is usually
employed. This aqueous composition is then placed in contact with
an electrically conductive anode and an electrically conductive
cathode in an electric circuit. While in contact with the bath
containing the coating composition, an adherent film of the coating
composition is deposited on the cathode.
The conditions under which the electrodeposition is carried out
are, in general, similar to those used in electrodeposition of
other types of coatings. The applied voltage may be varied greatly
and can be, for example, as low as one volt or as high as several
thousand volts, although typically between 50 volts and 500 volts
are usually employed. The current density is usually between about
0.25 ampere and 15 amperes per square foot and tends to decrease
during electrodeposition.
The method of the invention is applicable to the coating of any
conductive substrate and especially metal, such as steel, aluminum,
copper and the like. After deposition, the coating is cured at
elevated temperatures by any convenient method, such as in baking
ovens or with banks of infrared heat lamps. Curing temperatures of
at least 100.degree. C., and usually 125.degree. to 185.degree. C.
for at least 10 minutes and usually for about 10 to 30 minutes are
employed.
One of the advantages of the pigment grinding vehicles of the
present invention is the excellent corrosion resistance they impart
to cationic electrodeposited coatings over untreated steel or oily
steel substrates, even when the coatings are cured at relatively
low temperatures, i.e. 175.degree. C. and below, typically
160.degree.-175.degree. C.
Illustrating the invention are the following examples which are not
to be construed as limiting the invention to their details. All
parts and percentages in the examples, as well as throughout the
specification, are by weight, unless otherwise specified.
Example I
This example shows the preparation of a quaternary ammonium salt
group-containing material formed from reacting in the presence of
acetic acid, a polyglycidyl ether of bisphenol A with
N-dodecyldimethylamine.
______________________________________ Ingredients Parts by Weight
in Grams ______________________________________ ARMEEN DM18D.sup.1
418.5 Glacial acetic acid 84.6 Deionized water 35.25 EPON 828.sup.2
265 2-Butoxyethanol 378.3 ______________________________________
.sup.1 N--octadecyldimethylamine available from Armak Chemical Div.
.sup.2 Polyglycidyl ether of bisphenol A having an epoxy equivalent
of 18 commercially available from Shell Chemical Co.
The ARMEEN DM18D, 100 grams of the 2-butoxyethanol and the
deionized water were charged to a properly equipped reaction
vessel, heated to 50.degree. C., followed by adding the acetic
acid. The resultant mixture was allowed to react for a period of 15
minutes over a temperature range of 45.degree. to 55.degree. C.
Thereafter, at about 51.degree. C., the EPON 828 and the remaining
2-butoxyethanol were added and the mixture heated to 75.degree. C.,
and held over a temperature range of 75.degree. to 85.degree. C.
for 41/2 hours. The resultant mixture was cooled and stored.
Example II
This example shows the preparation of a quarternary ammonium salt
group-containing material formed from reacting in the presence of
lactic acid a polyglycidyl ether of bisphenol A with
N-octadecyldimethylamine and an amine containing alkyarylpolyether
moieties.
______________________________________ Ingredients Parts by Weight
in Grams ______________________________________ MONDUR TDS.sup.1 87
TRITON X-102.sup.2 386 Dimethylethanolamine 42 ARMEEN DM18D 141 88%
Lactic acid 111 Deionized water 88 EPON 828 220 2-Butoxyethanol 443
______________________________________ .sup.1 2,4Toluene
diisocyanate, available from Mobay Chemical Corp. .sup.2 An
alkylarylpolether of the structure ##STR5## where x = 12 to 13,
commercially available from Rohm and Haas Company.
The MONDUR TDS was charged to a properly equipped reaction vessel,
stirred and provided with a nitrogen blanket. Addition of the
TRITON X-102 was begun and continued by dripping it into the
reaction vessel at such a rate that the reaction temperature stayed
over the range of 25.degree.-35.degree. C. Upon completion of the
addition of the TRITON X-102, the reaction mixture was allowed to
react for 30 minutes over a temperature range of
30.degree.-40.degree. C., and then heated to 50.degree. C.
Thereafter, the dimethylethanolamine was dripped into the reaction
vessel with a resulting exotherm to 73.degree. C. Upon completion
of this addition, the reaction mixture was allowed to react for 45
minutes over a temperature range of 55.degree.-65.degree. C. (An
infrared scanning showed that all the isocyanate had reacted.) The
ARMEEN DM18D was melted and then added to the reaction mixture at
58.degree. C. This was followed by addition of the 88% lactic acid
with a resulting exotherm to 66.degree. C. The reaction mixture was
stirred for 30 minutes over the temperature range of
50.degree.-60.degree. C. The deionized water was added and the
reaction mixture held for 60 minutes over the temperature range of
50.degree.-60.degree. C. Thereafter, at 46.degree. C., the EPON 828
and 2-butoxyethanol were added to the reaction which exothermed to
70.degree. C. The reaction mixture was held for 41/2 hours over the
temperature range of 70.degree.-75.degree. C. to complete the
reaction. The reaction mixture was cooled and stored.
Example III
This example illustrates the preparation of a quaternary ammonium
salt group-containing material formed from reacting in the presence
of lactic acid a polyglycidyl ether of an aliphatic polyol with
N-octadecyldimethylamine and an amine containing alkylarylpolyether
moieties. The Example also shows the use of these resins as pigment
grinding vehicles.
______________________________________ Ingredients Parts by Weight
in Grams ______________________________________ MONDUR TDS 87
TRITON X-102 386 Dimethylethanolamine 42 ARMEEN DM18D 141 88%
Lactic Acid 111 Deionized water 88 ARALDITE RD-2.sup.1 153
2-Butoxyethanol 407 ______________________________________ .sup.1
Diglycidyl ether of 1,4butanediol, available from CibaGeigy Co.
The above ingredients were reacted in essentially the same manner
as described in Example II. The resultant composition was employed
as a pigment grinding vehicle in preparing a pigment paste. The
following were used in the preparation:
______________________________________ Ingredients Parts by Weight
in Grams ______________________________________ Aluminum silicate
clay 446.4 Lead silicate 72.1 Carbon black 57.5 Dibutyltin oxide
20.1 Deionized water 440.5 Grinding vehicle 60.5
______________________________________
The grinding vehicle was blended with the above pigments and the
deionized water to form a slurry which was ground in a Jiffy mill
for 2 hours to a Hegman 7.sup.+ grind.
A cationic paint comprising a blend of the above pigment paste and
an electrodepositable resinous film-forming composition was
prepared as follows. The electrodepositable resinous film-forming
composition was prepared with the following:
______________________________________ Parts by Ingredients Weight
in Grams ______________________________________ EPON 829.sup.1
727.6 PCP-0200 268.4 Xylene 36.1 Bisphenol A 197.8
Benzyldimethylamine 3.8 Capped isocyanate crosslinker.sup.2 933.5
Diketimine derived from diethylene 73.4 triamine and methyl
isobutyl ketone (73% solids in methyl isobutyl ketone)
N--methylethanolamine 59.1 2-Hexoxyethanol 76.5 Acetic acid 33.5
Cationic dispersant.sup.3 29.4 Deionized water 1793.1
______________________________________ .sup.1 Epoxy resin solution
made from reacting epichlorohydrin and bisphenol A having an epoxy
equivalent of 188, commercially available fro Shell Chemical Co.
.sup.2 Polyurethane crosslinker formed from halfcapping toluene
diisocyanate (80/20 2,4/2,6-isomer mixture) with 2ethylhexanol and
reacting this product with trimethylolpropane in a 3:1 molar ratio.
The crosslinker is present as a 70 percent solids solution in a
90/10 mixture of methyl isobutyl ketone and nbutanol. .sup.3 The
cationic dispersant was prepared by blending 120 parts of an alkyl
imidazoline commercially available from Geigy Industrial Chemicals
as GEIGY AMINE C, 120 parts by weight of an acetylenic alcohol
commercially available from Air Products and Chemicals Inc. as
SURFYNOL 104, 120 parts by weight of 2butoxyethanol, 221 parts by
weight of deionized water and 19 parts of glacial acetic acid.
The EPON 829, PCP-0200 and xylene were charged to a reaction vessel
and heated with a nitrogen sparge to 210.degree. C. The reaction
was held at reflux for about 1/2 hour to remove water
azeotropically. The reaction mixture was cooled to 150.degree. C.
and the bisphenol A and 1.6 parts of the benzyldimethylamine
(catalyst) added. The reaction mixture was heated to
150.degree.-190.degree. C. and held at this temperature for about
11/2 hours and then cooled to 130.degree. C. The remaining portion
of the benzyldimethylamine catalyst was added and the reaction
mixture held at 130.degree. C. for 21/2 hours until a reduced
Gardner-Holdt viscosity (50 percent resin solids solution in
2-ethoxyethanol) of P was obtained.
The polyurethane crosslinker, the diketimine derivative and the
N-methylethanolamine were then added and the temperature of the
reaction mixture brought to 110.degree. C. and held at this
temperature for 1 hour.
The 2-hexoxyethanol was added and the reaction mixture was
dispersed in water by adding the reaction mixture to a mixture of
the acetic acid, deionized water and the cationic dispersant. This
dispersion was diluted to 32 percent solids with deionized water
and vacuum stripped to remove organic solvent to give a dispersion
having a solids content of 36 percent.
The above electrodepositable composition and pigment pastes were
blended to form a cationic paint having a pigment to binder ratio
of 0.2 and a bath solids content of 20 percent. The paint had a
conductivity of about 1280 .mu.mhos/cm after ultrafiltration, and
pH was adjusted with acetic acid to 6.2. Steel panels were
electrodeposited in the paint at 275 volts for 2 minutes at a paint
temperature of 25.degree. C. The coated panels were baked at
170.degree. and 182.degree. C. for 20 minutes to obtain hard,
glossy and smooth coatings having a film thickness of about 0.4 to
0.7 mils.
Comparative Example
For comparison, steel panels were electrocoated with a paint
similar to the paint of Example III with the exception of the
pigment grinding vehicle used. The pigment grinding vehicle is the
reaction product of EPON 828 and a tertiary amine salt containing
blocked isocyanate groups. The vehicle is described in Example II
of U.S. Pat. No. 4,007,154. The pigments of Example III were ground
with this vehicle to form the paste.
The comparative paint had a pigment to binder ratio of 0.2 and a
solids content of 20 percent by weight as with the paint of Example
II. Steel panels were electrodeposited in the paint at 275 volts
for 2 minutes at a paint temperature of 25.degree. C. The coated
panels were baked at 171.degree. and 182.degree. C. for 20 minutes
to obtain hard, glossy, smooth coatings having a film thickness of
about 0.4 to 0.5 mils.
Panels coated with the cured paint of Example III were compared
with panels coated with the cured paint of the comparative example.
The paint of Example III was adjusted with 2-butoxyethanol (36
grams per gallon of paint) so as to equal the solvent content of
the paint of the Comparative Example.
The comparison was between corrosion resistance properties. The
coated panels were scribed with an "X" mark and placed in a salt
spray chamber at 100.degree. F. (38.degree. C.) at 100 percent by
weight relative humidity atmosphere of 5 percent by weight aqueous
sodium chloride solution for a period of 14 days. After 14 days,
the creepage from the scribe mark was measured and reported as
shown in Table I below.
TABLE I ______________________________________ Electrocoat Scribe
Creepage in microns At: Paint Containing: 182.degree. C./20 minutes
171.degree. C./20 minutes ______________________________________
Evaluation of Salt Spray Testing on Cold Rolled Steel Comparative
Example 1.6 4.7 Example III 0.8 2.3 Evaluation of Salt Spray
Testing on Oily Steel Comparative Example 7.8 9.4 Example III 4.7
4.7 ______________________________________
The above specific illustrations and other descriptions herein are
not intended to limit the scope of the invention. Instead, it is
intended that the invention include all the variations and
modifications falling within the scope of the appended claims.
* * * * *